It is well known in the art to provide vehicles with windshield wipers and windshield washers. In modern vehicles, the windshield washer nozzles are often mounted on the wiper blades so that they spray more of the washer fluid on the windshield where it is desired and inject less into the vehicle slipstream. Examples of various windshield wiping-washing arrangements are described in Patents GB 430366 to Rawlinson, U.S. Pat. No. 2,961,168 to Webb, U.S. Pat. No. 3,213,493 to Chichester, U.S. Pat. No. 3,230,564 to McDevitt, U.S. Pat. No. 6,234,410 B1 to Martin et al, and U.S. Pat. No. 6,082,636 to Yoshida et al. A wiper de-icing system is described in U.S. Pat. No. 6,438,789 B1.
FIG. 1 is a simplified representation of prior art vehicle windshield wiping-washing system 20 comprising windshield 22 and wiper assemblies 24, 24′. Wiper assembly 24 has oscillating wiper arm spindle 25, wiper arm 26, wiper blade support bracket 27, wiper blade 28 and spray nozzles 29 that emit spray 30 during the windshield washing mode. For convenience of explanation it is assumed that wiper assembly 24′ is functionally identical to wiper assembly 24. FIG. 1 illustrates windshield wiping-washing system 20 during a typical prior art windshield wiping-washing operation while wiper assemblies 24, 24′ are moving in directions 32, 32′ while emitting washing fluid spray 30.
FIG. 2 is a simplified flow chart showing operating process 60 of prior art vehicle windshield wiping-washing system 20 of FIG. 1. Process 60 begins with START 61, which usually occurs on vehicle power-up. In WASH SWITCH ON ? query step 62, it is determined whether the operator has pressed the “wash windshield” switch or button (usually found on the wiper control stalk). If the outcome of query 62 is NO (FALSE) then as shown by path 62A, process 60 loops back to start 61. If the outcome of query 62 is YES (TRUE), this initiates the windshield washing cycle. START PUMP step 63 is executed causing the washer fluid pump to turn on and WW ON IN WINDSHIELD WASH MODE step 64 to be executed. (The abbreviation “WW” stands for “windshield wiper”.). In step 64 causes the wipers to begin moving across the windshield, usually in a low speed mode, suitable for a wash cycle. WASH SWITCH STILL ON ? query 65 is then executed to determine whether the operator is still activating the “wash” switch. If the outcome of query 65 is YES (TRUE) then method 60 loops back as shown by path 65A and the pump and windshield wipers remain on. If the outcome of query 65 is NO (FALSE), then STOP PUMP step 66 is executed and the washing fluid pump shuts off, thereby terminating spraying of the windshield with washing fluid. The combination of steps 62-65 cause nozzles 29 to emit washing fluid spray 30 onto the windshield as long as the operator is activating the “wash” switch. After STOP PUMP step 66 washing fluid no longer flows to nozzles 29 and WW ON IN WINDSHIELD DRY MODE FOR TIME t1 step 67 is executed to dry the windshield for time duration t1. In step 67 the windshield wipers may be left in the same mode set in step 64 or changed to a different operating mode. The duration t1 may be selected by the designer, depending upon particular vehicle's requirements. Following the expiration of time duration t1, method 60 executes RETURN WW TO PRIOR MODE step 68 whereby it returns operation of the wipers to whatever state or mode they were in prior to initial query 62. Method 60 then returns to start 61 and initial query 62 as shown by path 69.
These systems generally work well as far as cleaning the windshield is concerned. However, present day wiper-washer systems still suffer from a number of limitations or disadvantages. A significant problem with such systems is that they permit ice build-up on the wiper blades during cold weather driving conditions. When that happens, the wipers blades tend to lose contact with the windshield because the ice can prevent the blade from flexing to follow the contour of the windshield. When this happens the wiping and/or washing action of the blades becomes progressively less effective. A smeared windshield and reduced visibility can result. This is a significant disadvantage. A limitation of prior art blade de-icing arrangements is that they are more complicated and more expensive that is desired.
Accordingly, it is desirable to provide an improved wiper-washer system that minimizes or eliminates blade icing in cold conditions. In addition, it is desirable that the blade de-icing apparatus and method be simple, rugged, reliable and require minimum modification of existing vehicle systems. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.